3BSE000860R1 SB510 ABB

Proportional control

The output value of the controller has a proportional relationship with the measured value and the set value of the controlled parameter or the deviation of a certain reference point.The proportional control is smoother than the two-position control,which eliminates the up and down oscillation of the controlled variable that occurs during the two-position control.For example,for the liquid level of a reaction tank,if the set liquid level value is 2700 mm,when the liquid level decreases,the valve on the feeding pipeline will increase the opening degree,and when the liquid level is high,it will be opened.degree decreased.The ratio of increase and decrease is proportional to the difference between the liquid level and the set value.

比例控制

控制器的输出值与被控参数的测量值和设定值或某个参考点的偏差是一个比例关系。比例控制比二位控制要平滑一些，消除了二位控制时会产生的被控量上下振荡的情形。比如，对一个反应罐的液位，如果设定的液位值是2700毫米，当液位降低时，进料管道上的阀门就要增加开度，而液位偏高时，则要将开度减小。增加和减小的比例与液位和设定值的偏差大小成比例关系。